Sleep, which takes up one-third of a person's life, is an important behavior for humans. However, in recent years, the influences of inadequate exercise in addition to stress and disruption of the daily rhythm of life, such as the inversion of night and day due to shifting of the hours of activity, have lead to an increase in the number of people complaining of inadequate sleep or insomnia, especially among city dwellers. Presently, it is said that one in five people have some form of dissatisfaction concerning sleep and one in ten people complain of insomnia of no less than one month. According to a field study concerning sleep disorders, the economic loss of Japanese citizens due to traffic accidents, etc., caused by sleep disorders is estimated at 1.4 trillion yen per year. It is furthermore estimated that for the nation of Japan as a whole, citizens spend 500 billion yen a year in medical expenses concerning sleep disorders, with medical costs spent on just sleeping drugs amounting to at least 182.5 billion yen.
The effects that various natural components have on sleep are widely known. For example, cedrol, which is a fragrance component that is contained in a conifer, such as Japanese cypress, cedar, etc., has been reported to have the effect of restraining the sympathetic nerves and making parasympathetic activity dominant and, in regard to sleep, is recognized to elongate the total sleeping time, shorten the sleep latency time, and increase the sleep efficiency (Patent Document 1). It is known that valerian, which is a Western herb, has a sedative effect and has been confirmed by human clinical tests to decrease the sleep latency time, improve the quality of sleep, elongate slow-wave sleep etc., (Non-Patent Document 1, Non-Patent Document 2).
Also, in tests using rats, Korean ginseng extract, which is widely used as a Chinese herbal medicine, has been reported to exhibit a sleep promoting effect, the effect of returning sleep, which has been changed in rhythm due to fasting, to a normal state, etc., (Non-Patent Document 3, Non-Patent Document 4). Furthermore, it has been reported that when 1-oleoyl-2-DHA-sn-3-phosphocholine, which is a phosphatidylcholine (PC) having DHA bonded to the sa-2 position and which, among the phosphatidylcholines contained in salmon roe oil, is a principle functional component in regard to sleep, is administered to a rat, the total sleeping time within 24 hours, the REM sleeping time, and the REM sleeping time with respect to the total sleeping time are increased (Non-Patent Document 5).
However, the abovementioned cedrol, which is a fragrance component of cedar, is a volatile substance and is thus difficult to use in the form of a food or medical drug that is taken orally. Also, research and development have not progressed much in regard to the details of the sleep improvement effects of valerian, Korean ginseng extract, and phosphatidylcholine.
[Non-Patent Document 1] Peter D. Leatherwood, Francoise Chaffard, Eva A Heck and Raphael Munoz-Box: Aqueous Extraction of Valerian Root (Valeriana offcinalis L.) improving Sleep Quantity in Man, Pharmacology Biochemistry & Behavior, Vol 17, pp. 65-71, 1982
[Non-Patent Document 2] Olov Lindahl and Lars Lindwall, Double Blind Study of a Valerian Preparation, Pharmacology Biochemistry & Behavior, Vol 32, pp. 1065-1066, 1989
[Non-Patent Document 3] Young Ho Rhee, Sung Pil Lee, Kazuki Honda, and Shojiro Inoue: Panax ginseng Extract Modulates Sleep in Unrestrained Rats, Psychopharmacology, 101, pp. 486-488, 1990
[Non-Patent Document 4] Sung Pil Lee, Kazuki Honda, Young Ho Rhee and Shojiro Inoue: Chronic Intake of Panax ginseng, Extract Stabilizes Sleep and Wakefulness in Food-deprived Rats, Neuroscinence Letters, 111, pp 217-221, 1990
[Non-Patent Document 5] Hidehiko Hibino, PC-DHA and Sleep, Food Style 2, Vol. 7, No. 3, pp. 50-53, 2003
[Patent Document 1] Republished Patent Publication No. WO01/058435